It is well known to use multi-cylinder air compressors on freight and passenger locomotives to supply compressed air to the operating and control equipment of a railway air brake system. During the operation of the air compressor, the discharge temperature of the compressed air tends to rise due to the heat of compression of the air. If there is insufficient cooling, the increased temperature of the air compressor amnd lubricating oil may cause the lubricating oil to break down resulting in an increase in viscosity. The increased viscosity of the lubricating oil can cause premature frictional wear and/or scoring of the cylinders and the compression and oil rings so that increased oil consumption occurs and results in frequent repair and maintenance. In addition, the maximum amount of moisture that pure air contains is dependent upon its temperature, pressure, and relative humidity. It will be appreciated that the higher the temperature of the air and relative humidity, the greater is the amount of moisture that it will contain and that the higher the pressure of the air, the smaller the amount of moisture that it will contain. It has been found that, when air is compressed, the rise in temperature due to the compression far more than offsets the opposite effect of the rise of pressure on the moisture-carrying capacity of the air. Therefore, water is precipitated by the cooling compressed air as it passes from the compressor to the various portions of the air brake system. Let us assume that a certain amount of atmospheric air enters a compressor at 100% relative humidity where it contains all the moisture possible at the existing outside temperature and ambient pressure. As this air is compressed and the temperature of air increases, its moisture-carrying capacity rapidly increases with the increased temperature, consequently, all the moisture is retained by this air and passes with it into the main or storage reservoir. Now if this compressed air is permitted to pass from the storage reservoir into the various parts and devices of the air supply system before being cooled to the outside ambient temperature, it will carry more moisture than it is capable of holding when the temperature finally drops to the normal point, and this excess moisture will be deposited because the pressure being high, the air cannot hold as much moisture as it did at the same temperature and at atmospheric pressure. Accordingly, in order to reduce the moisture to a minimum, it is advantageous to cool the air to the outside ambient temperature before it leaves the reservoir, thereby causing it to deposit all the excess moisture which can be quickly and easily removed by a suitable drain valve or cock. It is recommended practice on many railroads that the temperature of the compressed air in the main reservoir must be at the atmospheric ambient temperature and the condensate must be drained before being conveyed to the various downstream brake parts or components in order to prevent rust, scale, and corrosion in the control valves, cocks, gages, strainers, collectors, operating cylinders, etc. Accordingly, it has been recommended that the size and length of cooling or radiation pipe needed to keep moisture out of the main reservoir system should be that required to bring the temperature of the compressed air to within five degrees Fahrenheit (5.degree. F.) of ambient temperature upon its entrance to the number two (No. 2) reservoir when the air compressor is operating on a load-unload cycle to deliver eighty (80) cubic feet of free air per minute. It has been found that the temperature in the No. 2 main reservoir should be at or very near ambient temperature. Thus, it is very important to have the main reservoir air cooled to as close to the ambient temperature so that when the air is expanded to a lower pressure for operating the downstream brake equipment and auxiliary devices, it will be dry and remain dry if any further cooling is encountered. From an operational standpoint, it is very important that no free water be allowed to reach the braking devices since water causes corrosion, results in the formation of sludge and washes away lubrication and in winter or cold weather freezes to cause malfunctions of the brake equipment. It will be appreciated that it is usually not very practical and extremely expensive to continually add more or a sufficient amount of two inchs (2") iron pipe to the main reservoir system to reduce the compressed air to within 5.degree. F. of the surrounding ambient temperature before the air is permitted to enter the No. 2 main reservoir.